Gimbals Fins and SAS

[Daveroski]

Maybe I missed the memo, could someone tell me what happened?

Gimbals, control surfaces and SAS seem to fight each other for control each of them trying to correct the other ending with a ship that seems to move more side to side than vertical. They bend all over the place and then break apart.

Without SAS I get stable vertical flight until I try to turn. Then there is no stopping it from turning once it starts so I have to turn SAS on to stop it. Then it acts like its on elastic. After 3000 hours of play, I have never had so much difficulty.

Straight up and down multistage, Asparagus, Onion... Someone for pity's sake give me the memo!

Edited May 8, 2015 by Daveroski

[Ape_Descendant]

I have no where near that many hours but I have noticed thatI, more often than not, need to lock the gimbals (certanly on the bigger engines) to avoid the rocket attempting a hula hoop dance everytime I change direction.

[Mister Dilsby]

Yeah, you have to be careful how many different controls are working at once, because I do NOT think they have been optimized to work together. The special problem of 1.0 and onward is that drag in atmosphere now depends somewhat on orientation of the ship. So, as one control system tries to correct it, it creates an oscillation that a second control system tries to correct, perhaps in a much more violent way. The first control system tries to respond, they feed into each other until something breaks.

My advice is turn on the minimum number of control inputs to maintain heading. Think about which inputs are coarse adjustment (gimbal, big aero surfaces) and which are fine (SAS torque). And if you're not doing so already, stay away from SAS direction headings like prograde hold, those are all under-damped.

[Kelderek]

I don't know if this was new with 1.0, but you can adjust how much gimbal your engines have with a slider. In the VAB I usually reduce this to about 20% for all of the engines in my lifter stages. Add some fins near the bottom of your rocket, make sure you use plenty of struts to keep the "joints" (read: decouplers) sturdy, and make sure you have a high CoM. Don't deviate far from the prograde marker and you should be able to have a smooth flight.

The gimbal sliders seem to be the most help, set them low, but do not lock the gimbal.

[Daveroski]

The answer is clearly more struts.